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A129475 Primes of Erdos-Selfridge class 15+. 7
23869461181, 39279010921, 45608421601, 58345550881, 64788537493, 79681330633, 83807064853, 86315197987, 91658731403, 97331927117, 102581556673, 104758832257, 106426256653, 111136152961, 111795382441, 125586978001, 143216767091, 144155203267, 144708098881 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(1..19) calculated using A129474 up to 75e9, which gives A129475(20) > 150e9. This is enough to ensure that 288310406533 = A005113(16).

LINKS

Table of n, a(n) for n=1..19.

FORMULA

{ a(n) } = { p = 2*m*A129474(k)-1 | k=1,2,3... and m=1,2,3... such that p is prime and m has no factor of class > 14+ }

EXAMPLE

23869461181 = 1+2*7*1704961513, where 1704961513 is in A129474

PROG

(PARI) class(n, s=1) = { if(!isprime(n), 0, if(!(n=factor(n+s)[, 1]) || n[ #n]<=3, 1, for(i=2, #n, n[1]=max(class(n[i], s)+1, n[1])); n[1]))}

nextclass(a, s=1, p, n=[])={if(!p, p=nextprime(a[ #a]+1)); print("producing primes of class ", 1+class(a[1], s), ["+", "-"][1+(s<0)], " up to 2*", p); for(i=1, #a, for(k=1, p/a[i], if(isprime(2*k*a[i]-s), n=concat(n, 2*k*a[i]-s)))); vecsort(n)}

A129475=nextclass(A129474)

CROSSREFS

Cf. A129474, A005113.

Sequence in context: A297005 A233841 A015399 * A172612 A293624 A238356

Adjacent sequences:  A129472 A129473 A129474 * A129476 A129477 A129478

KEYWORD

nonn

AUTHOR

M. F. Hasler, Apr 16 2007

EXTENSIONS

Extended to a(19) by M. F. Hasler, Jan 12 2014

STATUS

approved

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Last modified April 18 14:43 EDT 2019. Contains 322209 sequences. (Running on oeis4.)